Summary:This paper summarizes the preliminary results of two independent clinical trials conducted with the preparation 'Ukrain'. containing thiopnosphoric acid alkaloid derivatives from the plant Chelidonium majus L (greater celandine), in order to investigate whether it has immunopotentiating properties in cancer patients. A total of twenty-seven patients with various malignancies were treated with "Ukrain" given intravenously in a dose of 10mg every three days. In all patients the cellular and humoral immune response was studied. There was an increase in both total T-cells and T-helper lymphocytes, a decrease in T-suppressor cells, and normalization of the helper/suppressor (HIS) ratio. A significant increase in erythrocyte—roselle-forming T-cells. and NK cells was also demonstrated. Serum immunoglobulin levels, complement components (C3 and C4), and acute phase proteins were not significantly enhanced. Restoration of cellular immunity was accompanied by an improvement in the patients' performance status and in the clinical course of the disease. The treatment was generally well tolerated. The present study shows that some therapeutic benefit from the use of Chelidonium majus ("Ukrain") as an immunostimutant in cancer patients can be achieved.